Molecular monitoring of hematologic malignancies: current and future issues

Genetic markers associated with hematologic malignancies such as acute promyelocytic leukemia (APL) can be detected with high sensitivity and specificity using the reverse-transcription polymerase chain reaction (RT-PCR). This procedure can be applied to monitor minimal residual disease. In patients with APL, RT-PCR is now being used to detect molecular relapse, and a strong association has been found between outcome and the treatment of molecular as opposed to hematologic relapse. In APL, results from PCR assays are also being used to guide therapy. Prognostic groups can be defined using molecular and clinical characteristics of the disease as well as patient characteristics. In the future, PCR monitoring strategies may be adapted to the risk of relapse of individual patients. Patients at high risk of relapse may be monitored much more rigorously than patients at low risk of relapse. Although RT-PCR is in routine use as a clinical tool, the lack of standardization of techniques in different laboratories has resulted in some difficulties in interpretation of results. There is a real need for an international consensus on standardization of PCR techniques.